Back to EveryPatent.com
United States Patent |
5,027,484
|
Baba
|
July 2, 1991
|
Tension controller for warping machine and warping method
Abstract
A tension controller for a warping machine maintains a constant yarn
tension during a warping operation from the beginning to the end of the
warping operation. The tension controller has a brake force control
mechanism (240) for controlling the size of the tension applied to the
running yarns, and a yarn speed control mechanism (290) for controlling
the running speed of the yarns. The brake control input, which is supplied
to the yarns brakes, and the running speed of the yarns are so controlled
that the actual yarn tension conforms to set or desired tension. When the
diameters of the yarn packages are relatively large, a brake force is
applied to the yarns, which run at a constant speed, thereby maintaining a
constant yarn tension. When the diameters of the yarn packages are
relatively small, on the other hand, a constant yarn tension is maintained
by reducing the running speed of the yarns while supplying a zero or
constant brake force to the yarns.
Inventors:
|
Baba; Yoshihiro (Osaka, JP)
|
Assignee:
|
Baba Sangyo Kikai Co., Ltd. (Osaka, JP)
|
Appl. No.:
|
471836 |
Filed:
|
January 29, 1990 |
Foreign Application Priority Data
Current U.S. Class: |
28/185; 28/194 |
Intern'l Class: |
D02H 013/14 |
Field of Search: |
28/172,185,194,245
|
References Cited
U.S. Patent Documents
4819310 | Apr., 1989 | Beerli et al. | 28/185.
|
4916783 | Apr., 1990 | Hagewood et al. | 28/172.
|
Foreign Patent Documents |
12235 | Jun., 1980 | EP | 28/185.
|
3206272 | Sep., 1983 | DE | 28/185.
|
61-275436 | Dec., 1986 | JP.
| |
62-238838 | Oct., 1987 | JP.
| |
Primary Examiner: Schroeder; Werner H.
Assistant Examiner: Calvert; John J.
Attorney, Agent or Firm: Fasse; W. G., Kane, Jr.; D. H.
Claims
What is claimed is:
1. A tension controller for a warping machine for maintaining a constant
tension of running yarns during a warping operation wherein a number of
yarns drawn out from a respective number of packages is symmetrically
arranged and wound on a warper's beam or drum, said tension controller
comprising:
brake force supply means (4, 250) for applying a brake force to said
running yarns within a predetermined range of a brake control input for
increasing yarn tension;
tension measuring means (220) for measuring an actual tension of said
running yarns;
set tension storage means (211) for storing information representing a
desired yarn tension;
tension comparing means (10, 280) for comparing said actual yarn tension
measured by said tension measuring means with said desired yarn tension
stored in said set tension storage means to provide a yarn tension
difference signal;
brake control input judging means (260) for judging whether or not an
actual brake control input to said brake force supply means has reached a
limit within said predetermined range and to provide a respective brake
control reference signal;
brake force control means (240) for controlling the value of said brake
control input to said brake force supply means (4, 250) to remove a
difference between said actual yarn tension and said desired yarn tension
in response to said yarn tension difference signal provided by said
tension comparing means and in response to said brake control reference
signal signifying that said actual brake control input has not yet reached
said limit; and
yarn speed control means (9A, 10, 290) for controlling the running speed of
said yarns to remove a difference between said actual yarn tension and
said desired yarn tension in response to said yarn tension difference
signal and in response to said brake control reference signal signifying
that said actual brake control input has reached said limit.
2. The tension controller of claim 1, further comprising:
yarn speed measuring means (270) for measuring the actual running speed of
yarns to provide an actual yarn running speed signal;
set speed storage means (212) for storing information representing a
desired yarn running speed; and
speed comparing means (280) for comparing said actual yarn running speed
signal with said desired yarn running speed stored in said set speed
storage means to provide a yarn speed difference signal in response to
said brake control signal signifying that said actual brake control input
has reached said limit, said yarn speed control means (290) comprising:
yarn speed increase means (291) for increasing said running speed of said
yarns in response to said yarn speed difference signal signifying that
said actual running speed is smaller than said desired running speed, and
yarn speed reducing means (292) for reducing the running speed of said
yarns in response to said yarn speed difference signal signifying that
said actual running speed is larger than said desired running speed.
3. The tension controller of claim 2, wherein
said brake force control means (240) comprises:
brake force increase means (241) for increasing said brake control input to
said brake force supply means in response to said tension difference
signal signifying that said actual tension is smaller than said desired
tension, and
brake force reducing means (242) for reducing said brake control input to
said brake force supply means in response to said tension difference
signal signifying that said actual tension is larger than said desired
tension.
4. The tension controller of claim 3, wherein
said brake force increase means (241) increases said brake control input to
said brake force supply means in response to said brake control reference
signal signifying that said actual brake control input has reached a lower
limit and in response to an indication by said speed comparing means that
said actual yarn running speed is identical to said desired running speed.
5. The tension controller of claim 3, wherein
said brake force reducing means (242) reduces said brake control input to
said brake force supply means in response to said brake control reference
signal signifying that said actual brake control input has reached the
upper limit and in response to said yarn speed difference signal
signifying that said actual yarn running speed is identical to said
desired running speed.
6. The tension controller of claim 1, wherein
said yarn speed control means (290) comprises drive means for changing the
speed of rotation of said warper's beam or drum in a continuous manner.
7. A warping method for systematically arranging a number of yarns drawn
out from a respective number of packages and winding said yarns on a
warper's beam or drum, said method comprising the steps of:
controlling an application of a brake force to running yarns for conforming
an actual yarn tension to a predetermined desired yarn tension;
determining whether said brake force control alone achieves said conforming
to provide a respective conforming or non-conforming signal, and
additionally controlling the running speed of said yarns in response to
said nonconforming signal signifying that said actual yarn tension cannot
be conformed to said desired yarn tension only by said controlling of said
brake force, thereby conforming said actual yarn tension to said desired
yarn tension by a combined control of said brake force and of said running
speed.
8. A warping method for systematically arranging a number of yarns drawn
out from a respective number of packages and winding said yarns on a
warper's beam or drum, comprising the steps of:
maintaining a constant yarn tension by supplying a brake force to said
yarns while driving said yarns to run at a constant speed when diameters
of said packages are relatively large, and maintaining a constant yarn
tension by reducing said running speed of said yarns while supplying a
zero or constant brake force to said yarns when diameters of said packages
are relatively small.
9. A warping method for systematically arranging a number of yarns drawn
out from a respective number of packages and winding said yarns on a
warper's beam or drum, comprising the following steps:
maintaining a constant yarn tension by controlling the running speed of
said yarns while applying a constant brake force to said yarns for
increasing tension on said yarns when diameters of said packages are
relatively large, and further maintaining a constant yarn tension by
controlling said brake force applied to said yarns while causing said
yarns to run at a constant speed when diameters of said packages are
relatively small.
10. A warping method for systematically arranging a number of yarns drawn
out from a respective number of packages and winding said yarns on a
warper's beam or drum, comprising the following steps:
maintaining a constant yarn tension by controlling the running speed of
said yarns while applying a constant brake force for increasing tension on
said yarns in an initial stage when diameters of said packages are
relatively large,
maintaining a constant yarn tension by controlling a brake force applied to
said yarns while causing said yarns to run at a constant speed in an
intermediate stage of yarn package filling status, and
maintaining a constant yarn tension by controlling the running speed of
said yarns while applying a constant brake force for increasing tension on
said yarns in a final stage where diameters of said packages are
relatively small.
Description
FIELD OF THE INVENTION
The present invention relates to a tension controller for a warping machine
such as a beam warper, a drum warper or the like. The invention also
relates to a warping method.
DESCRIPTION OF THE BACKGROUND ART
BACKGROUND INFORMATION
Warping machines and sizing machines are known as machines for preparing
yarns for weaving. A warping machine is adapted to systematically arrange
a number of yarns which are drawn out from a number of packages held by
creels and wind the same on a warper's beam or drum. A sizing machine is
adapted to size warps which are drawn out from a number of warper's beams,
dry and wind the same on a sizing beam.
In general, natural or blended yarns are prepared for a weaving process
through a warping process and a sizing process. Synthetic yarns may be
directly brought into the weaving process through the warping process with
no sizing.
The warping operation is adapted to arrange a number of warps in parallel
with each other for making a woven fabric, and hence it is most important
to maintain a uniform tension of the yarns which are wound on the warper's
beam or drum. To this end, various types of tension controllers have been
recently proposed for maintaining a constant tension of the yarns in the
warping operation.
Japanese Patent Publication (Laying-Open No. 62-238838, Application No.
62-82188) with a claim of priority based on Swiss patent application No.
1286/86-8, discloses a technique which is of interest to the present
invention. Japanese Patent Publication No. 62-238838 also corresponds to
U.S. Pat. No. 4,819,310. FIG. 1 of the above publication illustrates a
tension controller for a drum warper. A number of yarns 103 are drawn out
from a number of bobbins 102, which are held by a creel 101, and wound on
a warper's drum 107 by a brake force supplier 104, a measuring roller 105
and a deflection roller 106. The measuring roller 105 measures the total
tension of the number of yarns 103 passing through the same. The brake
force supplier 104 supplies the running yarns 103 with a running
resistance, i.e., brake force, thereby increasing the yarn tension. In
order to maintain a constant tension of the running yarns 103, the brake
control input of the brake force supplier 104 is adjusted in response to
the actual yarn tension which is detected by the measuring roller 105. The
yarns 103 are driven to run at a constant speed.
Even if the brake control input of the brake force supplier 104 is zero,
the running yarns 103 are subjected to tension, which is caused by the
release resistance in relation to the bobbins 102 and the air resistance
against the running yarn.
The inventor has examined the relationship between changes of a package
diameter and the yarn tension. FIG. 2 shows on the ordinate the yarn
tension (g) or changes thereof caused when cotton yarns of count No. 40
were drawn out from parallel packages at a speed of 800 m/min, as a
function of the package diameter (mm) plotted on the abscissa. As
understood from FIG. 2, the yarn tension is lowered with as the package
diameter is reduced in the first half where the package diameter is large.
In the second half of FIG. 2 where the package diameter is small, on the
other hand, the yarn tension is increased as the package diameter is
further reduced to reach the maximum value immediately before the packages
are used up.
Due to the relation between the package diameter and yarn tension shown in
FIG. 2, it is impossible to maintain a constant yarn tension from
beginning to end of the warping operation, by using the tension controller
disclosed in the above mentioned Japanese Patent Publication No.
62-238838. It is assumed here that the yarn tension is set at 20 g in FIG.
2, for example. In that case, the brake force supplier 104 supplies the
yarns with tension T.sub.1, which is evaluated by subtracting yarn tension
T.sub.0 in the case of a zero brake control input from the set tension (20
g). The brake force supplier 104 is adapted to apply tension to the
running yarns, but is not able to reduce the yarn tension which is caused
by a release resistance in relation to the package diameters and air
resistance against the running yarn. Referring to FIG. 2, therefore, it is
possible to control the actual yarn tension to the set tension to conform
by adjusting the brake control input by the brake force supplier 104 until
the package diameter is about 45 mm. When the package diameter falls below
about 45 mm, however, the actual yarn tension is inevitably increased
beyond the set tension even if the brake control input by the brake force
supplier 104 is zero.
With reference to FIG. 2, the set tension may be so selected as to maximize
the yarn tension T.sub.0 which is caused by the release resistance in
relation to the packages and by air resistance against the running yarn,
i.e., at about 23 g. In order to select the set tension at such a value,
however, it is necessary to considerably increase the brake control input
of the brake force supplier 104. In other words, excessive tension T.sub.2
is regularly applied to the running yarns. Hence, the yarns are weakened
and frequently breakage or disconnection of the yarn occurs.
Thus, it is extremely difficult to maintain a constant yarn tension from
beginning to end of the warping operation by the tension controller
disclosed in Japanese Patent Publication No. 62-238838, i.e., a tension
controller which adjusts the tension applied to the yarns only by the
brake control input to the brake force supplier.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a tension controller
for a warping machine, which can maintain a constant tension of the
running yarns from the beginning to the end of the warping operation.
Another object of the present invention is to provide a tension controller
for a warping machine, which can maintain the brake control input by a
brake force supplier at a relatively low level.
Still another object of the present invention is to provide a warping
method which can maintain a constant tension of the running yarns from the
beginning to the end of the warping operation.
The tension controller for a warping machine according to the present
invention, comprises brake force supply means, tension measuring means,
set tension storage PG,7 means, tension comparing means, brake control
input judging means, brake force control means and yarn speed control
means. The brake force supply means applies a brake force to the running
yarns within a predetermined range of brake control input values to
increase the yarn tension. The tension measuring means measures the actual
tension of the running yarns. The set tension storage means stores
received information representing a set or desired tension for the yarns.
The tension comparing means compares the actual yarn tension measured by
the tension measuring means with the set or desired yarn tension stored in
the set tension storage means. The brake control input judging means
judges or determines whether or not the actual brake control input by the
brake force supply means, has reached a value within the limits of the
predetermined range. The brake force control means controls the value of
the brake control input by the brake force supply means, to remove a
difference between the actual yarn tension and the set yarn tension in
response to a comparing made by the tension comparing means showing that
the actual yarn tension is different from the set yarn tension and to a
determination made by the brake control input judging means indicating
that the actual brake control input has not yet reached the limit. Thus,
the yarn speed control means controls the yarn running speed to remove the
difference between the actual yarn tension and the set yarn tension.
In the warping method according to the present invention, the brake force
is applied to the running yarns to conform the actual yarn tension to a
predetermined set yarn tension. When it is impossible to conform the
actual yarn tension to the set yarn tension with only the brake force, the
yarn running speed is so controlled that the actual yarn tension to the
set tension conforms.
In one aspect of the present warping method, a constant yarn tension is
maintained by applying a brake force to the yarns to run at a constant
speed when the package diameter is relatively large. When the package
diameter is relatively reduced as the warping progresses, the yarn running
speed is reduced while applying no brake force or constant brake force to
the yarns.
On the one hand according to the present invention, the yarn tension is
adjusted only by the brake operation if the tension of running yarns can
be conformed to a predetermined set tension only by a respective operation
of the brake force supply means. On the other hand, if the yarn tension
cannot be conformed to the predetermined set tension only by the operation
of the brake force supply means, the yarn tension is conformed to the
predetermined set tension by adjusting the yarn running speed. Therefore,
the yarn tension can be maintained at a relatively low level as compared
with the conventional tension controller which controls the yarn tension
only by the operation of the brake force supplier. Thus, it is possible to
reduce the frequency of breakage or disconnection in the warping and
during subsequent steps without lowering yarn strength by an excessive
yarn tension. Further, a constant yarn tension can be maintained from the
beginning to the end of the warping operation. In addition, the yarns can
be uniformly wound at the set tension without reference to the material
and thickness of the yarns, the size of the packages, the speed for
winding the yarns and the like. Thus, skill is not required for driving
the warping machine, and uniform warper's beams can be obtained at a high
quality without personal errors caused by operators.
These and other objects, features, aspects and advantages of the present
invention will become more apparent from the following detailed
description of the present invention when taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a tension controller for a warping machine, as disclosed
in a Japanese Patent Publication No. 62-238838;
FIG. 2 illustrates the result of an examination of the relationship between
the package diameter and the yarn tension;
FIG. 3 illustrates the result of an examination of the relationship between
the yarn running speed and the yarn tension;
FIG. 4 is a block diagram showing an embodiment of the yarn tension control
of the present invention;
FIG. 5 is a flow chart showing an operation for controlling the yarn
tension;
FIGS. 6, 7, 8 and 9 illustrate the relationships between the brake control
input to the brake force supply means, the yarn running speed, and the set
yarn tension;
FIG. 10 is a schematic plan view showing an embodiment of the present
invention;
FIG. 11 is a side elevational view of the warping machine shown in FIG. 10;
FIG. 12 is a perspective view showing an example embodying brake force
supply means; and
FIGS. 13A, 13B, 13C, 13D and 13E are schematic plan views illustrating the
relationships between running yarns and brake force supply means
respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The inventor has made a test by changing the running speed of yarns, which
were drawn out from packages and wound on a warper's beam, without any
application of a brake force to the yarns, for measuring changes in the
yarn tension. FIG. 3 shows the result of the measurements made during the
test. The horizontal axis shows the running speed of the yarns, and the
vertical axis shows the yarn tension. The test was made with parallel
packages of cotton yarns of count No. 20. As understood from FIG. 3, the
yarn tension increases substantially proportionately to an increase in the
yarn running speed. The inventor has noted this phenomenon, to achieve the
present invention.
FIG. 4 is a schematic block diagram showing a tension controller for a
warping machine according to an embodiment of the present invention.
Referring to FIG. 4, the present tension controller comprises input means
200 for inputting control information information storage means 210 for
storing information representing a set or desired yarn tension, tension
measuring means 220, tension comparing means 230 for comparing a set
tension with a measured tension to provide a yarn tension difference
signal, brake force control means 240, brake force supply means 250, brake
control input judging means 260 for providing a brake control reference
signal, yarn speed measuring means 270, speed comparing means 280 for
providing a speed difference signal, and yarn speed control means 290. The
present tension controller maintains a constant tension of a number of
running yarns, which are drawn out from a number of packages held by
creels, in a warping operation for systematically arranging the yarns and
winding the same on a warper's beam or drum.
The brake force supply means 250 applies a controlled brake force to the
running yarns which are drawn out from the packages i.e., to cause a
running resistance or an additional tension, within a range predetermined
by the control input, to increase the yarn tension. The brake force supply
means 250 may be formed by means which can simultaneously supply the brake
force to a number of yarns. For example, the brake force supply means 250
can be formed by a tension washer which is pressed by springs, or a bar
tension mechanism which is provided with a plurality of parallel bars for
changing the degree of bending of the yarns by moving an intermediately
positioned bar. The tension added to the yarns is increased or decreased
in response to an increase or decrease of the control input of the brake
force supply means 250. Even if the control input by the brake force
supply means 250 is zero, the running yarns are subjected to tension which
is caused by the release resistance by the yarns against being pulled out
of the packages and by air resistance against the running yarns, as
hereinabove described.
The tension measuring means 220 measures the actual yarn tension of the
running yarns. More specifically, the tension measuring means 220 measures
the total or average tension of the overall yarns which are wound on the
warper's beam of a beam warper or the drum of a drum warper. This tension
measuring means 220 is preferably a detecting roller contacting the yarns
to angularly bend passages thereof for detecting the pressure applied to
this detecting roller.
Set or desired information as to the number of the yarns to be warped, the
desired yarn tension, the desired yarn speed, an initial brake control
input and the like are inputted through the input means 200 and stored in
the information storage means 210. The set information storage means 210
comprises set tension storage means 211 for storing the received
information of the set yarn tension and set speed storage means 212 for
storing the received information of the set yarn running speed.
The tension comparing means 230 compares the actual yarn tension measured
by the tension measuring means 220 with the set yarn tension stored in the
set tension storage means 211.
The brake control input judging means 260 judges whether or not the actual
brake control input by the brake force supply means 250 has reached a
limit within a predetermined range.
The brake force control means 240 controls the brake control input to the
brake force supply means 250 for removing a difference between the actual
yarn tension and the set or desired yarn tension in response to the output
of the tension comparing means 230 indicating that the actual measured
yarn tension is different from the set yarn tension and in response to an
output from the brake control input judging means 260 that the actual
brake control input has not yet reached the required limit. This brake
force control means 240 comprises brake force increase means 241 for
increasing the brake control input if the actual tension is smaller than
the set tension, and brake force reducing means 242 for reducing the brake
control input if the actual tension is larger than the set tension.
The yarn speed control means 290 controls the yarn running speed to remove
a difference between the actual yarn tension and the set yarn tension in
response to a recognition made by the tension comparing means 230 that the
actual yarn tension is different from the set yarn tension and a
recognition made by the brake control input judging means 260 that the
actual brake control input has reached the limit.
The yarn speed measuring means 270 measures the actual yarn running speed.
This yarn speed measuring means 270 comprises a speed detecting roller
which is arranged in frictional contact with the surface of a layer of
yarns which are wound on the warper's beam or drum, for example, and a
pulse generator which outputs a pulse signal every rotation of the speed
detecting roller.
The speed comparing means 280 compares the actual yarn running speed
measured by the yarn speed measuring means 270 with the set running speed
stored by the set speed storage means 212 in response to a recognition
made by the brake control input judging means 260 that the actual brake
control input has reached the limit.
The aforementioned yarn speed control means 290 comprises yarn speed
increase means 291 and yarn speed reducing means 292. The yarn speed
increase means 291 increases the yarn running speed in response to a
recognition made by the speed comparing means 280 that the actual running
speed is smaller than the set running speed. The yarn speed reducing means
292 reduces the yarn running speed in response to a recognition made by
the speed comparing means 280 that the actual running speed is larger than
the set running speed. The yarn speed control means 290 can be formed by a
drive unit 9A for rotating or driving the warper's beam or drum 9, see
FIG. 10. Such a drive unit is preferably able to wind the yarns on the
warper's beam or drum at a constant speed and to change the speed in a
continuous manner if needed for example, the drive unit can be formed by a
mechanism having motor with a drive shaft coupled to the warper's beam
through a continuous speed change gear. Another suitable drive mechanism
may comprise an adjustable speed motor connected to a drive shaft of the
warp beam or drum. Still another driven mechanism may comprise a driving
drum contacting the warper's beam under pressure to rotate or drive the
beam at a constant speed. The speed of the driving drum can be varied
conventionally if needed.
The operation of the tension controller will now be described with
reference to FIGS. 4 and 5. Referring to FIG. 5, the symbol T.sub.s
denotes the set yarn tension. The symbol T.sub.a denotes the actual yarn
tension. The symbol S.sub.s denotes a set yarn. The symbol S.sub.a denotes
the actual yarn. The symbol B denotes the actual brake control input. The
symbol B.sub.max denotes the upper limit of the brake control input, and
the symbol B.sub.min denotes the lower limit of the brake control input.
Before starting the warping operation, set information as to the number of
yarns to be warped, the initial brake control input, the desired yarn
tension T.sub.s, the desired yarn speed S.sub.s, and the like is inputted
into the set or desired information storage means 210 (step S1) by the
operator.
When the warping operation is started, the tension measuring means 220
measures the actual yarn tension T.sub.a, and the tension comparing means
230 compares the actual yarn tension T.sub.a with the set yarn tension
T.sub.s (step S2).
If the actual yarn tension T.sub.a is smaller than the set yarn tension
T.sub.s, a decision is made whether or not the actual brake control input
B has reached the limit within the predetermined range (step S3).
If the brake control input B is within the predetermined range but has not
yet reached the desired limit, the brake force increase means 241
increases the brake control input by the brake force supply means 250, to
approach the actual yarn tension T.sub.a to the set yarn tension T.sub.s
(step S4).
Thereafter, it is confirmed whether or not the warping operation for the
current lot is completed (step S5). If the warping operation is not yet
completed, the process returns to the step S2. If the warping operation
for the lot is completed, the tension control is stopped.
If it is recognized at step S3 that the actual brake control input B has
reached the upper limit B.sub.max, the yarn speed increase means 291
increases the yarn running speed to conform the actual yarn tension
T.sub.a to the set yarn tension T.sub.s (step S6).
If it is recognized at step S3 that the actual brake control input B has
reached the lower limit B.sub.min, on the other hand, the speed comparing
means 280 compares the actual yarn speed S.sub.a with the set yarn speed
S.sub.s (step S7). If the actual yarn speed S.sub.a is smaller than the
set yarn speed S.sub.s, the yarn speed increase means 291 increases the
yarn speed (step S6). If it is recognized that the actual yarn speed
S.sub.a is identical to the set yarn speed S.sub.s, the brake force
increase means 241 increases the brake control input by the brake force
supply means 250 (step S4).
If it is recognized at step S2 that the actual yarn tension T.sub.a is
larger than the set yarn tension T.sub.s, a decision is made whether or
not the actual brake control input B by the brake force supply means 250
has reached the limit of the predetermined range (step S8).
If it is recognized that the actual brake control input B is within the
predetermined range but has not yet reached the desired limit, the brake
force reducing means 242 reduces the brake control input B by the brake
force supply means 250 to conform the actual yarn tension T.sub.a to the
set or desired yarn tension T.sub.s (step S9).
If it is recognized at step S8 that the actual brake control input B has
reached the lower limit B.sub.min, the yarn speed reducing means 292
reduces the yarn running speed to conform the actual yarn tension T.sub.a
to the set or desired yarn tension T.sub.s (step S10).
If it is recognized at step S8 that the actual brake control input B has
reached the upper limit B.sub.max, on the other hand, the actual yarn
speed S.sub.a is compared with the set or desired yarn speed S.sub.s (step
S11). If the actual yarn speed S.sub.a is larger than the set yarn speed
S.sub.s, the yarn speed reducing means 292 reduces the yarn running speed
(step S10). If it is recognized that the actual yarn speed S.sub.a is
identical to the set or desired yarn speed S.sub.s, on the other hand, the
brake control input by the brake force supply means 250 is reduced (step
S9).
If it is recognized at the step S2 that the actual yarn tension T.sub.a is
identical to the set or desired yarn tension T.sub.s, it is confirmed
whether or not the warping operation for the lot is completed (step S5).
Referring to FIG. 6, the horizontal axis shows the package diameter and the
left vertical axis shows the yarn tension, while the right vertical axis
shows the yarn running speed. The curve A shows the yarn tension which is
measured when the brake control input to the brake force supply means 250
is zero and the yarn running speed is fixed at the set or desired speed
V.sub.O. The point A.sub.a shows a brakeless tension caused the release
resistance of the yarn out of a full packages and the air resistance. The
point A.sub.b shows a brakeless tension caused by the release resistance
developed immediately before the packages are used up and the air
resistance. The straight line T.sub.N shows the set or desired yarn
tension, and the straight lines V.sub.O and V.sub.b show the actual yarn
speeds. The letter T denotes the value of additional tension which is
supplied to the yarns by operating the brake force supply means 250. In
other words, the tension T is evaluated by subtracting the tension shown
in the curve A from the set tension T.sub.N.
In the state shown in FIG. 6, the set or desired yarn tension T.sub.N is
lower than the maximum value A.sub.b of the brakeless tension A. The lower
limit of the operation range is set at such a control input that the
additional tension T supplied by the brake force supply means 250 is zero,
while the letter C denotes the intersection between the straight line
showing the set tension T.sub.N and the curve A showing the brakeless
tension. Until the package diameter reaches the x-coordinate of the
intersection C, i.e., until the brake control input by the brake force
supply means 250 reaches the lower limit of zero, the tension T is added
to the brakeless tension A by operating the brake force supply means 250,
to provide the set or desired tension T.sub.N. During this period, the
yarn running speed shown in the right vertical line is maintained at the
initial value V.sub.0. When the curve A passes through the intersection C,
i.e., when the package diameter is further reduced beyond the intersection
C, the brakeless tension A exceeds the set tension T.sub.N. Therefore, the
additional tension T is fixed at the minimum value and the yarn running
speed is reduced along the oblique line V.sub.b, thereby maintaining the
actual yarn tension at the set or desired tension T.sub.N.
In the example shown in FIG. 6, the additional tension T applied by the
brake force supply means 250 has such a wide variable range that its upper
limit, i.e., the maximum additional tension, is larger than the difference
between the set tension T.sub.N and the minimum value of the brakeless
tension A. On the other hand, FIG. 7 shows an example wherein additional
the tension T applied by the brake force supply means 250 has a narrow
variable range.
Referring to FIG. 7, T.sub.max denotes the maximum value within the
variable range of the additional tension T which is applied by the brake
force supply means 250. In the first half of FIG. 7 where the package
diameter is still large, the total tension B of the brakeless tension A
and the maximum additional tension T.sub.max is smaller than the set
tension T.sub.N. At this stage, the brake control input of the brake force
supply means 250, i.e., the additional tension T, is fixed at the maximum
value. The yarn running speed is increased from the initial value V.sub.0
to follow an upwardly curved line V.sub.a. As hereinabove described, the
tension acting on the yarns is increased or decreased with an increase or
decrease of the yarn running speed. Therefore, the total of the brakeless
tension A, the maximum additional tension T.sub.max applied by the brake
force supply means 250 and the tension which is increased or decreased
with an increase or decrease of the yarn running speed is caused to
conform to the set tension T.sub.N, as shown in FIG. 7.
When the package diameter is reduced as the warping operation progresses,
the total B of the brakeless tension A and the maximum additional tension
T.sub.max applied by the brake force supply means 250 exceeds the set
tension T.sub.N. In this case, the yarn running speed is fixed at the
initial value V.sub.0 and the brake control input of the brake force
supply means 250 is adjusted, as shown in FIG. 7. Thus, the actual yarn
tension is caused to conform to the set tension T.sub.N.
When the package diameter is further reduced, so that the brakeless tension
A reaches the set or desired tension T.sub.N and the additional tension T
applied by the brake force supply means 250 reaches zero at a point C, the
yarn running speed is reduced along an oblique line V.sub.b, to conform
the actual yarn tension to the set tension T.sub.N.
FIG. 8 shows an example of a warping operation of thick yarns. In order to
warp thick yarns, the set or desired tension T.sub.N is so increased that
the yarns are not loosened by their own weight. In the first half of FIG.
8 where the package diameter is still large, therefore, the total B of
brakeless tension A and the maximum additional tension T.sub.max applied
by the brake force supply means 250 has not yet reached the set or desired
tension T.sub.N. In this stage, the additional tension T supplied by the
brake force supply means 250 is fixed at the maximum value T.sub.max, and
the yarn running speed is increased from its initial value V.sub.0 to
initially follow an upwardly curved line V.sub.a. Thus, the actual yarn
tension is caused to conform to the set tension T.sub.N. When the package
diameter is so reduced that the total tension B exceeds the set or desired
tension T.sub.N, i.e., when the total tension B enters the variable range
of the additional tension T, the actual tension is maintained at the set
or desired tension T.sub.N by controlling the additional tension T for
fixing the yarn running speed at the initial value V.sub.0.
In the examples shown in FIGS. 6 to 8, the brakeless tension A.sub.a, which
is caused by the release resistance developed when the yarns are drawn out
from a full packages at the set speed V.sub.0 and the air resistance, is
smaller than the set tension T.sub.N. In an initial stage of a warping
operation, however, the brakeless tension A.sub.a may be larger than the
set or desired tension T.sub.N, as shown in FIG. 9. In this case, the
actual tension is caused to conform to the set tension T.sub.N by reducing
the brake control input to the minimum value of zero and by increasing the
yarn running speed along an oblique line V.sub.a up to a point D, i.e.,
until the brakeless tension A of the initial stage reaches the set or
desired tension T.sub.N. The initial speed of the yarns is smaller than
the set or desired speed V.sub.0. In the interval between the point D and
a point C shown in FIG. 9, the yarn running speed is fixed at the set
speed V.sub.0, and the additional tension T is added to the brakeless
tension A by operating the brake force supply means 250. The additional
tension T is fixed at the minimum value of zero when the same passes
through the point C, and the yarn running speed is reduced along another
oblique line V.sub.b.
FIGS. 10 and 11 illustrate the structure of the embodiment of an present
invention, including a warping machine 1 and left and right creels 2. Each
of the creels 2 is provided with a number of vertically and horizontally
arranged packages 3. A number of yarns Y is drawn out from the number of
packages 3 and the yarns are guided through yarn brake devices 4 and guide
bars 5 toward guide rods 6a and 6b and a reed 6 of the warping machine 1.
Thereafter the yarns Y are wound on a warper's beam 9 through a measuring
roller 7 for detecting the tension and through a guide roller 8 for
changing the running direction. Bearings not shown for supporting both
ends of the measuring roller 7 are provided on a pressure sensor 7A,
having an output connected to a control unit 10. A speed detecting roller
11a is arranged to be in frictional contact with the surface of a layer of
the yarns wound on the warper's beam 9. A pulse generator 11b outputs a
pulse signal for each revolution of the speed detecting roller 11a and
transmits the pulse signal to the control unit 10.
A brake drive unit 12A for setting the brake control inputs of the yarn
brake devices 4 and a brake detector 12B for detecting the control inputs
are provided between the yarn brake devices 4 of the creels 2 and the
control unit 10. Further, an input unit 13 such as a keyboard is provided
in order to input set or desired values of the yarn tension, yarn speed
and control inputs for the yarn brake devices 4 in the control unit 10,
respectively. A drive unit 9A drives the warp beam 9.
FIG. 12 shows an exemplary yarn brake device 4 which is provided in the
creel 2. A hollow prismatic bar 22 is mounted on a front base plate 21 for
every vertical column of a number of vertically and horizontally arranged
packages 3. The bar 22 is provided on its front surface with a drop wire
unit including two yarn hooks 23a and 23b and an inverted U-shaped drop
wire 24, in correspondence to the package 3. When the warping machine is
driven, the drop wire 24 is raised up by the yarn Y to hold the drop wire
24 in the upright state shown in FIG. 12. When the yarn Y is broken, the
drop wire 24 is rotated downwardly counter clockwise about its lower end
24a. The bar 22 is provided in its interior with an electric contact,
which is closed when the drop wire 24 falls due to breakage of the yarn Y,
thereby stopping the operation of the warping machine 1.
At the back of the bar 22, first, second and third fixed tension bars 25a,
25b and 25c are mounted on the base plates 21, whereby these bars are
spaced apart from each other. A first slide plate 26a is slidably arranged
between the first and second fixed tension bars 25a and 25b. A first
movable tension bar 27a is secured on the first slide plate 26a. A second
slide plate 26b is also slidably arranged between the second and third
fixed tension bars 25b and 25c, and a second movable tension bar 27b is
secured on the second slide plate 26b. The upper ends of the tension bars
25a, 25b, 25c, 27a and 27b are supported by fixed and movable upper
support plates, respectively but not shown.
The first slide plate 26a is provided on its end with a rack 26c, which
engages with a pinion 28a. This pinion 28a is driven for rotation by a
motor not shown, which corresponds to the brake drive unit 12A for
controlling the yarn tension. The second slide plate 26b is also provided
on its end with a rack 26d, which engages with a pinion 28b. This pinion
28b is driven for rotation by an air cylinder, not shown. As shown in FIG.
12, the first to third fixed tension bars 25a to 25c are positioned on one
side of the running yarn Y, while the first and second movable tension
bars 27a and 27b are positioned on the other side of the running yarn Y.
FIGS. 13A to 13E illustrate relationships between the running yarn Y and
the tension bars. With reference to FIGS. 12 and 13A to 13E, the operation
and function of the movable tension bars 27a and 27b will now be
described.
When the warping operation progresses in a normal manner, the first and
second movable tension bars 27a and 27b are positioned as shown in FIG.
13A. When the warping machine 1 is stopped by breakage of the yarn or the
like, the air cylinder drives the pinion 28b, to slidingly move the second
slide plate 26b along an arrow a shown in FIG. 12. Consequently, the
second movable tension bar 27b is brought from the position shown by solid
lines to a position (27b) shown by phantom lines in FIG. 12. FIG. 13B
shows this state. The second movable tension bar 27b pushes the yarn Y to
extremely bend the same, thereby applying an excessive brake force to the
yarn Y and preventing the same from following gravity also referred to as
"inertial delivery". Japanese patent publication No. 61-275436 discloses a
mechanism for preventing such "inertial delivery" of yarns.
The first movable tension bar 27a adjusts the amount of pushing in response
to a brake control input of the yarn Y with respect to the first and
second fixed tension bars 25a and 25b, thereby adjusting the yarn tension
during running. FIG. 13C shows a state wherein the first movable tension
bar 27a responds to a large brake control input to supply a relatively
large tension to the yarn Y. FIG. 13D shows a state wherein the first
movable tension bar 27a responds to a relatively small brake control input
to apply a relatively small tension to the yarn Y. On the other hand, FIG.
13E shows a state wherein the brake control input of the first movable
tension bar 27a is zero, i.e., no tension is applied to the yarn Y.
Until the package diameter reaches the x-coordinate of the intersection C
shown in FIG. 6, for example, the brake control input changes the position
of the first movable tension bar 27a by a sliding movement of the first
slide plate 26a, to apply additional tension T to the yarn Y. When the
package diameter is reduced to reach the x-coordinate of the intersection
C, the brake control input for moving the first movable tension bar 27a,
reaches zero. FIG. 12 shows such a position of the first movable tension
bar 27a in phantom lines, which corresponds to the state shown in FIG.
13E. The yarn Y runs linearly in this state. When the tension of the yarn
Y is further increased beyond the set or desired tension, the first
tension bar 27a stands still in the position shown in FIG. 13E. In order
to conform the actual tension to the set or desired tension, the speed of
rotation of a drive motor 9A is reduced thereby to decrease the
circumferential speed of the warper's beam 9. Thus, an increase of the
tension is prevented, to maintain a constant tension on the yarn Y.
Although the present invention has been described and illustrated in
detail, it is clearly understood that the same is by way of illustration
and example only and is not to be taken by way of limitation, the spirit
and scope of the present invention being limited only by the terms of the
appended claims.
Top